Ultrasonic optical cleaning system

ABSTRACT

An ultrasonic optical cleaning system is provided for cleaning and deterring the buildup of organic and inorganic particulates from the surface of glassware used in water testing instrumentation. The system includes a transducer that is attached to the surface of the glassware. A connector cap carrying a plurality of spring contacts interconnecting the transducer with an ultrasonic transducer control circuit. The control circuit operates continuously to provide an electrical signal to the transducer that vibrates the transducer and the glassware so that the glassware is cleaned of contaminates.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/513,857 filed Oct. 24, 2003.

FIELD OF THE INVENTION

This invention relates to a system that ultrasonically cleans and detersthe buildup of particulate matter on glassware of the type used inoptical water testing equipment. The apparatus is particularly suitedfor use in cleaning a tube or cuvette that supports a water sample in aturbidimeter.

BACKGROUND OF THE INVENTION

Turbidimeters are widely utilized to test public water supplies for thepresence of particulate matter suspended in the water. Examples of theseinstruments include the turbidimeter disclosed in U.S. Pat. No.5,446,544, as well as the updated version distributed by HF Scientific,Inc. under the brand name MICRO TOL™. These and other varieties ofturbidimeters typically employ a glass cuvette or tube that holds thewater to be tested. Light is directed through the test sample andturbidity is electronically calculated and displayed.

Over time, inorganic particulates and organic contaminates such as algaetend to build up on the surface of the glassware holding the testsample. This can distort the measurements taken by the turbidimeter,which can produce erroneous readings. To avoid inaccurate test results,the user must frequently clean the glass and recalibrate theturbidimeter. This tends to be tedious, time consuming and inefficient.The user is likely to experience undesirable “down-time” as turbidityreadings cannot be taken while the instrument is being serviced.

Currently, a cuvette or other glassware used for optical testing ofwater must be cleaned manually on a periodic basis. There are no knowndevices available that automatically and continuously clean theglassware so that improved measurement accuracy is achieved, but tediousmaintenance and repeated service interruptions are avoided.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus for automatically and continuously cleaning and deterringparticulate build-up on the glassware that accommodates a test sample ina turbidimeter or other optical water-testing instrument.

It is a further object of this invention to provide an ultrasonicoptical cleaning system that significantly reduces the inefficiency,tedium and service interruptions associated with manual cleaning.

It is a further object of this invention to provide an apparatus forultrasonically cleaning turbidimeter glassware, which apparatus is nothard-wired to the electronics of the tubidimeter so that the glasswarecan be conveniently indexed and/or removed for recalibration, as needed.

It is a further object of this invention to provide an apparatus thateffectively and efficiently cleans the glassware used in a water-testinginstrument so that improved, accurate water quality measurements areobtained.

It is a further object of this invention to provide an apparatus forultrasonically cleaning a turbidimeter cuvette, which apparatus cleansand deters the buildup of both inorganic and organic contaminates sothat the user does not have to manually clean the glassware andrecalibration of the turbidimeter is significantly reduced.

This invention features an ultrasonic optical cleaning system for usewith glassware of the type used in optical water testing equipment. Thesystem includes an ultrasonic transducer that is secured to theglassware to be cleaned. The transducer includes a material thatvibrates when a selected voltage is applied to the transducer. Thetransducer is electrically connected to an ultrasonic control circuit bymeans of a contact connector cap. The ultrasonic control circuitdelivers an electrical signal through the connector cap to thetransducer so that the transducer vibrates to clean particulate matterfrom the glassware and prevent the build-up of particulates on thesurface of the glassware.

In a preferred embodiment, the ultrasonic transducer includes a diskcomposed of a piezoelectric ceramic that is juxtaposed against andbonded to a lower surface of an aluminum disk. Preferably, the aluminumdisk has a larger diameter than the piezoelectric disk. The surface ofthe aluminum disk opposite to the surface that carries the piezoelectricdisk may be bonded directly to the surface of the glassware, such as onthe bottom of the glassware. As a result, the piezoelectric disk facesaway from the surface of the glassware. The transducer is preferablysecured to the glassware by an appropriate adhesive.

The connector cap may include an upper portion that carries a pluralityof contacts for electrically engaging the transducer. These may bespring contacts that are longitudinally retractable within the connectorcap. An outer spring contact may be engagable with the aluminum disk andan inner spring contact may be interengagable with the piezoelectricdisk. The upper surface of the cap may also include an annular wall thatsurrounds the contacts for receiving a lower end of the glassware. Inthis way, the glassware is held in place with the transducer engagingthe contacts. Lower ends of the contacts may extend from a lower end ofthe connector cap and be wired or otherwise electrically connected tothe ultrasonic control circuit.

The ultrasonic control circuit may comprise an ultrasonic printedcircuit board that is operably mounted to the printed circuit board thatcontrols operation of the water testing equipment. The ultrasoniccontrol circuit may receive power from the principal operating circuitof the test equipment. The control circuit typically delivers a voltagethrough the connector cap to the transducer and sweeps through a seriesof frequencies over a predetermined time span. Typically, thefrequencies include the resonant frequency for the transducer-cuvetteassembly such that the transducer exhibits a maximum vibration andenergy is transferred to the glassware at a sufficient level so thatoptimum cleaning is achieved. Because the glassware is maintainedsubstantially free of organic and inorganic particulates, improvedmeasurements of water quality are obtained. At the same time,maintenance requirements are reduced considerably.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Other objects, features and advantages will occur from the followingdescription of a preferred embodiment and the accompanying drawings, inwhich:

FIG. 1A is side elevational view of the ultrasonic optical cleaningsystem of this invention as used with a turbidimeter;

FIG. 1 B is a cross sectional view of the cleaning system;

FIG. 2 is a perspective view of glassware comprising a cuvette and theultrasonic transducer in position to be applied to the cuvette;

FIG. 3 is a view similar to FIG. 2 with the ultrasonic transducer bondedto a lower surface of glassware;

FIG. 4 is a perspective top view of the connector cap;

FIG. 4A is an exploded view of the connector cap;

FIG. 5 is a bottom perspective view of the connector cap;

FIG. 6 is a plan view of the upper, component side of the main printedcircuit board employed in a turbidimeter featuring the cleaning systemof this invention; the ultrasonic printed circuit board is depicted asbeing mounted to the main board;

FIG. 7 is a plan view of the bottom, solder side of the main circuitboard with the connector cap of the cleaning system attached thereto;and

FIG. 8 is a schematic view of a preferred version of the ultrasoniccontrol circuit.

There is shown in FIGS. 1A and 1B an ultrasonic optical cleaning system10 used for cleaning the glassware of a turbidimeter. In the versiondisclosed herein, the glassware comprises a conventional cuvette 12 ofthe type commonly employed in water quality testing equipment. This typeof glassware may be used in a wide variety of optical instrumentationpresently used in the water testing industry. Cuvettes of this type areused especially widely in turbidimeters such as the product disclosed inU.S. Pat. No. 5,446,544 and the previously referenced MICRO TOL™turbidimeter. It should be understood, however, that cleaning system 10is not limited to use with such products. The cleaning system may beused effectively in a wide range of optical test instruments and issuitable for cleaning all types of liquid-accommodating glassware. Theparticular type of instrumentation that uses the cleaning system doesnot constitute a limitation of this invention. It should also be notedthat a wide variety of sizes and shapes of glassware may be utilized.These may include all types of glass cuvettes, tubes and other varietiesof transparent containers.

In the embodiment depicted in FIG. 1, cuvette 12 is carried by a flowhead 14, which comprises a part of a component of the tubidimeter(otherwise not shown). The cuvette is supported so that opticalmeasurements may be taken and turbidity determined by the instrument ina known fashion. Over time, organic and inorganic particulates tend tocollect on the surface of cuvette 12. These contaminates distort theoptical measurements taken by the turbidimeter; as a result, the cuvettenormally has to be cleaned manually on a frequent and periodic basis.Cleaning system 10 is specifically designed to reduce the need for suchperiodic cleanings and resultant “down-time” and to enable theturbidimeter to produce continuously accurate readings over a prolongedperiod of operation.

The cleaning system specifically includes an ultrasonic transducer 16,which is shown also in FIGS. 2 and 3. Transducer 16 includes arelatively large diameter aluminum disk 18 and a relatively smalldiameter piezoelectric ceramic (i.e. piezoceramic) disk 20 that isbonded to disk 18. More particularly, disk 20 is fastened to a lowersurface of disk 18 by means of a suitable adhesive. This may includeLoctite™ E-20HP epoxy or a similar product. Preliminarily, the lowersurface 22 of cuvette 12 is roughened by using a coarse sandpaper orsimilar product. At least an outer ring 24 of lower surface 22 shouldexhibit deep scratches that facilitate bonding. The bottom of thecuvette is then cleaned with alcohol. The upper surface of thetransducer (i.e. the upper surface of aluminum disk 18) is similarlycleaned. The adhesive is then applied between ring 24 of lower cuvettesurface 22 and the upper surface of aluminum disk 18. Adhesive shouldnot be applied to the lower surface of cuvette 12 within the areabounded by ring 24. The upper surface of the transducer is engagedagainst the lower surface of the cuvette and the adhesive is allowed tocure. As a result, the transducer is bonded to the lower surface ofcuvette 12 in the manner shown in FIG. 3.

As shown in FIGS. 1A and 1B, the lower end of cuvette 12 and theultrasonic transducer supported by the cuvette are received within aring or annular lip 30 of a connector cap assembly 32. The connector capassembly is shown alone in FIGS. 4, 4A and 5. In particular, theconnector cap includes a generally circular base 34 having a recessedlower surface 36, FIG. 5. Ring 30 extends upwardly from an upper surfaceof base 34. A plurality of holes 38 are formed through the base suchthat the upper surface of the base communicates with the recessed lowersurface of the base. Connector cap 32 is composed of a suitable plastic.Holes 38 reduce the amount of plastic required and also provide anemergency drain in the event of cuvette breakage.

Connector cap 32 includes an outer coil spring contact 40 and an innercoil spring contact 44. These comprise respective coil springs which aremounted in base 34 of cap 32 such that they are longitudinallyretractable relative to the base. The end posts 45 and 47 of springcontacts 40 and 44 respectively are received through respective holes49, 51 in base 34 and bent as shown in FIG. 5 to hold contacts 40 and 44in place. Each of the springs 40 and 44 is disposed within the areasurrounded by ring 30. As best shown in FIGS. 4 and 4A, the upper end53, 55 of each spring is ground flat for engaging transducer 16. Asshown in FIG. 5, the lower ends of the springs protrude from therecessed region 36 of cap 32 and are connected through associated wiringW to a transducer control circuit, as is described more fully below.Other types of contacts, and preferably spring contacts, may be utilizedwithin the scope of this invention.

As shown in FIG. 6, an ultrasonic printed circuit board 50 is secured tothe component side of the main printed circuit board 52 used to operatethe turbidimeter. Board 50 supports an ultrasonic transducer controlcircuit 60, shown in detail in FIG. 8. More particularly, the componentsof circuit 60 are mounted on ultrasonic printed circuit board 50 in aconventional manner. Circuit 60 is electrically interconnected betweenthe microcontroller and power supply of the main circuit board 52 andthe wiring W that joins circuit 60 to connector cap 32. (See FIGS. 7 and8).

The transducer control circuit includes a contact strip 70, FIG. 8,which has eight contact pins 1-8. Pins 1 and 8 are connected to andprovide power from the conventional principal power source (notexplicitly labeled) of the turbidimeter or other instrument. In thisversion, 15 volts are delivered to a high voltage circuit 72. Thiscircuit, which comprises a coil 74 and a MOSFET 76, increases thevoltage to approximately 48 VAC peak-to-peak for use by the transducerin a manner described below. Pin 2 of contact strip 70 provides a lowervoltage (e.g. 3.3 volts) to operate various components of controlcircuit 60 such as pulse width modulator 78, voltage controlledoscillator 80 and detection circuit 84.

Pin 6 of contact strip 70 provides a signal P4.5 from the CPU of theturbidimeter or other instrument to pulse width modulator 78, whichconverts the signal to DC voltage. This voltage is then delivered tooscillator 80, which functions as a voltage-to-frequency converter. Avariable frequency output signal, which varies between approximately 30and 55 KHz, is produced at output 5 of oscillator 80. This signal istransmitted to a buffer circuit 82, which controls the operation of gateG of transistor 76. As previously stated, circuit 72 increases theoutput voltage delivered from the main power source considerably. A highvoltage alternating current signal is thereby provided to pins 3 and 4of strip 70. The signal sweeps across the frequency range describedabove so that such a range of frequencies are delivered to thecomponents of transducer 16 over wiring W. This sweep is performed overa span of approximately thirty seconds. During that time, the resonantfrequency of the transducer-cuvette assembly is generated so that thetransducer vibrates especially vigorously and particulate matter isdislodged from the glass surface of the cuvette or other glassware.

Detection circuit 84 monitors operation of the transducer and provides asignal P6.3 to pin 7, which indicates a problem with the cuvette or thecleaning system. In particular, a drastic change in the voltage producedby circuit 84 may reveal that a cuvette is missing, that one or more ofthe contact springs are broken or that no contact is being made betweenthe springs and the transducer. Corrective action may then be taken.

It should be understood that in alternative embodiments, various othertypes of circuits and alternative electrical components known to personsskilled in the art may be employed to deliver an electrical signal tothe transducer so that the transducer is vibrated to clean the glasswarein the manner previously described. The particular components describedin this circuit and the frequency and voltage levels described hereinare intended to be illustrative only and do not constitute limitationsof the invention.

In operation, circuit 60 remains continuously “on” during use of theturbidimeter or other water testing instrumentation with which system 10is employed. As a result, a sweep of frequencies are delivered fromcontrol circuit 60 to transducer 16. As previously stated, thispreferably includes the resonant frequencies of the transducer-cuvetteassembly so that maximum vibration and optimum cleaning are achieved.More particularly, the transducer is supplied with a signal ofapproximately 50 volts (peak to peak) and the control circuit sweeps thefrequency between 30 and 55 KHz to assure that the resonant frequency ofeach individual transducer-cuvette assembly is generated. This providesfor maximal vibration and optimal cleaning of the glassware.

The use of the connector cap is particularly advantageous. The springsprovide for flexible and yet positive interengagement and electricalcontact between the control circuit and the transducer. As a result, thecontrol circuit does not have to be “hard wired” to the transducer. Theuser is thereby able to freely rotate and/or remove the cuvette from thetest instrument without having to remove or disengage wires orelectrical connectors. In the context of the turbidimeter referencedabove, it is also important for the user to periodically index thecuvette within the turbidimeter by axially turning the tubularglassware. Such indexing allows the turbidimeter to obtain the cleanestand most accurate readings through the glassware. The glassware alsomust be removed each time recalibration of the instrument is required.Because the cleaning system of the present invention is not hard wired,performing the necessary indexing (rotation) and glassware removal (forre-calibration) are facilitated considerably. When the glassware isindexed, the spring contacts simply slide across and remain in unbrokencontact with the transducer. Removing the glassware disengages thecontacts from the transducer and replacing the glassware after in theinstrument is calibrated automatically re-engages the spring contactswith the transducer. No wiring or connectors must be manipulated foreither procedure.

From the foregoing it may be seen that the apparatus of this inventionprovides for a system that automatically and continuously inhibits thebuildup and growth of organic and inorganic particulates on optical testequipment glassware so that more reliable readings may be taken withreduced interruption of service. While this detailed description has setforth particularly preferred embodiments of the apparatus of thisinvention, numerous modifications and variations of the structure ofthis invention, all within the scope of the invention, will readilyoccur to those skilled in the art. Accordingly, it is understood thatthis description is illustrative only of the principles of the inventionand is not limitative thereof.

Although specific features of the invention are shown in some of thedrawings and not others, this is for convenience only, as each featuremay be combined with any and all of the other features in accordancewith this invention.

Other embodiments will occur to those skilled in the art and are withinthe following claims:

1. A system for ultrasonically cleaning glassware in optical water testing equipment, said system comprising: an ultrasonic transducer for securing to the glassware to be cleaned, said transducer including material that vibrates when a selected voltage is applied to said transducer; a connector for establishing electrical contact with said transducer; and an ultrasonic control circuit for delivering an electrical signal with the selected voltage through said connector to said transducer such that said transducer vibrates to dislodge particulate matter from the glassware and prevent particulate matter from collecting on the surface of the glassware.
 2. The system of claim 1 in which said transducer including a piezoelectric disk and an aluminum disk juxtaposed against and secured to said piezoelectric disk.
 3. The system of claim 2 in which an upper surface of said aluminum disk is attachable to the glassware, said piezoelectric disk being secured to an opposite, lower surface of said aluminum disk.
 4. The system of claim 3 in which said transducer is attachable to the glassware by an adhesive.
 5. The system of claim 1 in which said connector includes a connector cap comprising a plurality of contacts for energizing said transducer.
 6. The system of claim 5 in which said contacts are slidably engagable with said transducer to maintain electrical contact with said transducer when said transducer and the glassware are adjusted in the testing equipment.
 7. The system of claim 5 in which said contacts comprise spring contacts carried by an upper portion of said cap for electrically engaging said transducer.
 8. The system of claim 7 in which said springs are longitudinally retractable within said cap.
 9. The system of claim 8 in which said spring contacts comprise coil spring contacts.
 10. The system of claim 2 in which said connector includes an outer coil spring contact that is interengagable with said aluminum disk and a second inner coil spring contact that is interengagable with said piezoelectric disk.
 11. The system of claim 5 in which said cap includes an annular wall surrounding said contacts for receiving said transducer and an attached lower end of the glassware, said wall for holding the glassware in place with said transducer engaging said contacts.
 12. The system of claim 7 in which lower ends of said spring contacts are electrically connected to said ultrasonic control circuit.
 13. The system of claim 1 in which said control circuit includes an ultrasonic printed circuit board for operably mounting to a printed circuit board that controls operation of the water testing equipment, said control circuit for being electrically powered by an operating circuit of the test equipment.
 14. The system of claim 1 in which said control circuit generates signals having a series of frequencies, including the resonant frequency of said transducer and glassware to which said transducer is attached such that said transducer and glassware vibrate sufficiently to maintain the surface of the glassware substantially free of particulate build-up.
 15. The system of claim 14 in which said control circuit continuously and repeatedly sweeps through a predetermined series of frequencies.
 16. The system of claim 1 in which said selected signal includes the resonant frequency of the transducer and glassware to which said transducer is secured. 